when i switched to ZIC 5000 from Delo Gold on my 115K clocked 2.0D with slightly weak engine, i felt the following changes:
1) morning startup improved...better sound and quicker startup
2) throttle response after the startup (esp in morning). I start the car and let it idle to bring to NOT and then drive out.
3) fuel efficiancy
4) smoke and sluggishness, that slowly increased in case of Delo Gold after driving 1500 kms, subsided. and the oil remained fresh till 3500 - 4000 kms (my usual ODI).
used it till the car clocked 135K after which I switched to a GLi now.
I used Leppon Oil filter (part no. 115C) which is slightly bigger (in legnth) than the one typically used in 2C's.